Aerospace balloon system and method of operation

ABSTRACT

A balloon system including a balloon, and optionally including a payload and/or a safety module. A balloon, preferably including a balloon envelope and one or more passive vents, and optionally including one or more active valves. A method of balloon system operation, preferably including maintaining a zero-pressure balloon condition and sealing balloon vents, and optionally including ascending, descending, and/or otherwise operating the balloon system in flight.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/164,668, filed 1 Feb. 2021, which claims the benefit of U.S.Provisional Application Ser. No. 62/969,447, filed 3 Feb. 2020, each ofwhich is incorporated in its entirety by this reference.

TECHNICAL FIELD

This invention relates generally to the aerospace vehicle field, andmore specifically to a new and useful aerospace balloon system andmethod of operation.

BACKGROUND

High-altitude zero-pressure balloons are typically vented to maintain azero-pressure state within the balloon. However, such venting istypically achieved via passive vents that fluidly couple the ballooninterior with the surrounding atmosphere. Thus, there is a need in theaerospace vehicle field to create a new and useful aerospace balloonsystem and method of operation.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a schematic representation of an embodiment of a balloonsystem.

FIG. 1B is a side view of an example of the balloon system in afully-inflated state.

FIGS. 1C-1D are side views of a first and second specific example,respectively, of the balloon system in a partially-inflated state.

FIGS. 2A-2B are side views of a first and second specific example,respectively, of a balloon of the balloon system.

FIG. 3A is a side view of a third specific example of the balloon.

FIG. 3B is a detail view of a portion of FIG. 3A.

FIG. 4A is a side view of a fourth specific example of the balloon,including a passive vent configured in a first configuration.

FIGS. 4B-4C are cross-sectional detail views of a portion of FIG. 4A,including the passive vent configured in the first configuration and asecond configuration, respectively.

FIGS. 5A-5B are schematic representations of a first example of aclosure mechanism of a passive vent in the first configuration and thesecond configuration, respectively.

FIGS. 5C-5D are schematic representations of a second example of theclosure mechanism in the first configuration and the secondconfiguration, respectively.

FIGS. 6A-6B are schematic representations of a third example of theclosure mechanism in the first configuration and the secondconfiguration, respectively.

FIGS. 7A-7B are schematic representations a fourth example of theclosure mechanism in the first configuration and the secondconfiguration, respectively.

FIG. 8 is a schematic representation of an embodiment of a method ofballoon system operation.

FIG. 9 is a schematic representation of an example of the method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments of the inventionis not intended to limit the invention to these preferred embodiments,but rather to enable any person skilled in the art to make and use thisinvention.

1. Overview

A balloon system 100 preferably includes a balloon 101, and canoptionally include a payload 102 and/or a safety module 103 (e.g., asshown in FIGS. 1A-1B). However, the balloon system 100 can additionallyor alternatively include any other suitable elements in any suitablearrangement. A method 200 of balloon system operation preferablyincludes maintaining a zero-pressure balloon condition S220 and sealingballoon vents S230 (e.g., as shown in FIGS. 8-9 ). The method 200 canoptionally include ascending S210, descending S240, and/or otherwiseoperating the balloon system in flight. However, the method 200 canadditionally or alternatively include any other suitable elementsperformed in any suitable manner.

2. Benefits

Embodiments of the balloon system 100 and/or method 200 can confer oneor more benefits. In some embodiments, the system and/or method canallow venting of lift gas from zero-pressure balloons at high altitudes,preferably while also preventing ingress of atmospheric gasses into suchballoons at lower altitudes (e.g., during descent from and/or ascent tohigher altitudes, etc.). Thus, such embodiments can enable safe flightoperation of a zero-pressure balloon (possibly a hydrogen-inflatedballoon, but additionally or alternatively a balloon inflated with anyother suitable lift gas), including descent from high altitudes (e.g.,stratospheric altitudes) into lower altitudes (e.g., troposphericaltitudes), while reducing or eliminating risks associated with such adescent (e.g., explosion risks arising from mixing hydrogen withingested air, buoyancy-loss risks arising from displacement of lift gasby ingested air, etc.). In contrast, typical aerospace balloon systemsare not designed to descend with an inflated balloon, but rather willdeflate the balloon and/or detach the payload from the balloon before orduring a payload descent (typically, in order to initiate the descent);accordingly, such systems would typically face these risks if used todescend while attached to an inflated balloon. However, the systemand/or method can additionally or alternatively confer any othersuitable benefits.

3. Balloon System

The balloon system 100 is preferably a balloon-based aerospace vehicle(e.g., balloon-propelled space capsule), such as a balloon-propelledvehicle configured to operate in the troposphere, stratosphere, and/orany other suitable atmospheric layers. However, the system canadditionally or alternatively be any other suitable lighter-than-airvehicle or aerostat (e.g., airship), space vehicle (e.g., spacecraftand/or space capsule), aerodyne (e.g., fixed- and/or rotary-wingaircraft), and/or any other suitable aerospace vehicle. In alternateembodiments, the system can additionally or alternatively function as aterrestrial vehicle, a watercraft, and/or any other suitable vehicle.

The system 100 can optionally include one or more elements such asdescribed in U.S. Provisional Patent Application 62/969,447, filed 3Feb. 2020 and titled “Space Capsule”, which is herein incorporated inits entirety by this reference. In examples, the balloon 101 can includeone or more elements described in U.S. Provisional Patent Application62/969,447 regarding the ‘Balloon System’, the payload 102 can includeone or more elements described in U.S. Provisional Patent Application62/969,447 regarding the ‘Capsule System’ and/or ‘Avionics and Power’,and/or the safety module 103 can include one or more elements describedin U.S. Provisional Patent Application 62/969,447 regarding the ‘BackupDescent System’. However, the system 100 can additionally oralternatively include any other suitable elements described in U.S.Provisional Patent Application 62/969,447.

3.1 Balloon.

The balloon 101 preferably includes an envelope 110 and one or morepassive vents 140, and can optionally include one or more active valves150, reefing sleeves, and/or any other suitable elements (e.g., as shownin FIGS. 1D, 2A-2B, 3A-3B, and/or 4A-4C). The balloon 101 preferablydefines an apex and a nadir. When the balloon is inflated and in flight,the apex is arranged at (or substantially at) the top of the balloon(e.g., with respect to a gravity vector), and the nadir is arranged at(or substantially at) the bottom of the balloon (e.g., opposing the apexacross the balloon along or substantially along the gravity vector).

The balloon is preferably a zero-pressure balloon (e.g., configured tomaintain a substantially zero-pressure configuration, in which theballoon interior is at substantially the same pressure as the atmospheresurrounding the balloon, while fully and/or substantially-fullyinflated; configured not to maintain a substantially greater pressurewithin the balloon than in the surrounding atmosphere; etc.). However,the balloon can alternatively be a super-pressure balloon or any othersuitable type of balloon.

In some embodiments, the balloon 101 (and/or elements thereof, such asthe envelope 110) can include one or more elements such as described inU.S. patent application Ser. No. 17/162,151, filed 29 Jan. 2021 andtitled “Aerospace Balloon System and Method of Operation”, which isincorporated in its entirety by this reference (e.g., as described inU.S. patent application Ser. No. 17/162,151 regarding the ‘balloon 101’and/or the ‘envelope 110’). For example, the balloon 101 can optionallyinclude an apex fitting and/or nadir fitting such as described in U.S.patent application Ser. No. 17/162,151, and/or the envelope 110 caninclude one or more gores, load members, and/or reinforcement elementssuch as described in U.S. patent application Ser. No. 17/162,151.

3.1.1 Envelope.

The envelope 110 preferably functions to contain a lighter-than-airfluid (e.g., lift gas, such as helium, molecular hydrogen, etc., and/ormixtures thereof). In some embodiments, the lighter-than-air fluid is aflammable fluid, preferably hydrogen gas (or a mixture containinghydrogen gas). However, the lighter-than-air fluid can additionally oralternatively include any other suitable species. The envelopepreferably contains enough fluid to fully or substantially fully inflatethe balloon while it is operating at or near the maximum altitude of aflight, more preferably containing an excess of such fluid during ascent(wherein this excess fluid can be referred to as ‘free lift’). Further,the envelope no preferably functions to isolate this lighter-than-airfluid from the surrounding atmosphere (e.g., preventing mixing ofoxygen-containing air with the fluid contained within the envelope).

The balloon will typically be partially deflated at lower altitudes, dueto the significantly increased atmospheric pressure at lower altitudes.For example, a zero-pressure balloon (e.g., in which thelighter-than-air fluid is at substantially the same pressure as theatmosphere surrounding the balloon) will typically not contain much morefluid than sufficient to be fully inflated (while in the zero-pressurecondition) at a maximum intended altitude, and thus will be onlypartially inflated at lower altitudes, at which the higher atmosphericpressure compresses that same quantity of fluid into a smaller volume(e.g., defining a volume ratio between the partially- and fully-inflatedballoon of less than 1%, 2%, 3%, 5%, 10%, 15%, 20%, 30%, 0.1-1%, 1-2%,2-5%, 5-10%, 10-20%, 20-30%, 30-50%, or greater than 50%).

3.1.2 Passive Vent.

The balloon 101 preferably includes one or more passive vents 140. Athigh altitudes (e.g., when the balloon is in the high-altitude range,such as described below), the passive vents preferably function tofluidly couple the balloon interior to the atmosphere, thereby enablingpassive maintenance of a zero-pressure condition within the balloon viapassive venting of lift gas. At lower altitudes, the passive vents arepreferably sealed to prevent ingress of atmospheric gases (e.g., oxygen)into the balloon interior. In examples, the passive vents can includeone or more elements such as described in U.S. Provisional PatentApplication 62/969,447, filed 3 Feb. 2020 and titled “Space Capsule”,which is herein incorporated in its entirety by this reference (e.g., asdescribed in U.S. Provisional Patent Application 62/969,447 regardingthe ‘Closable balloon vent ducts’ and/or the ‘Closable zero pressureballoon ducts’).

The passive vents 140 are preferably operable in two configurations. Inthe first configuration, the balloon interior is fluidly coupled to theballoon exterior (e.g., to the atmosphere) via the passive vent (e.g.,as shown in FIGS. 4A-4B, 5A, 5C, 6A, and/or 7A). In this configuration,the vent preferably defines an aperture in the balloon wherein lift gascan passively vent through the aperture. In the second configuration,the balloon interior is preferably not fluidly coupled to the balloonexterior via the passive vent (e.g., as shown in FIGS. 4C, 5B, 5D, 6B,and/or 7B). In this configuration, the aperture in the balloon ispreferably closed and/or sealed such that atmospheric gas cannot enterthe balloon through the aperture. The passive vent is preferablyoperable to transition from the first configuration to the secondconfiguration, and can optionally be operable to transition from thesecond configuration to the first configuration, to repeatedlytransition between the configurations, to transition into any othersuitable configurations, and/or be configured in any other suitablemanner. In other embodiments, each passive vent may be operable totransition once (and only once) from the first configuration to thesecond configuration and may not be operable to transition back to thefirst configuration. However, the passive vents can additionally oralternatively have any other suitable functionalities.

In a first embodiment, the passive vent includes a duct structure. Inthis embodiment, the vent defines an aperture 141 in the balloonenvelope, and the aperture is connected to an extended duct that (e.g.,in the first configuration) vents to atmosphere. In this embodiment, theduct runs from a balloon end 142 (connected to the aperture) to anexternal end 143 which vents to the atmosphere. The duct can be attachedto the balloon along all or part of its length (e.g., at or near theexternal end, at or near the balloon end, at any suitable locationbetween the ends, etc.), such as shown by way of example in FIG. 2A,and/or can hang freely down from the balloon, such as shown by way ofexample in FIGS. 2B and/or 3A-3B.

In a second embodiment, the vent is a simple opening. In thisembodiment, an aperture 141 (e.g., slit, hole, etc.) defined in theballoon envelope forms the vent. For example, the vent can define a holein the bottom of the balloon. In this embodiment, in the firstconfiguration, the aperture is open and leads directly between theballoon interior and exterior (e.g., atmosphere).

In a third embodiment, the vent includes a skirt structure. In thisembodiment, the balloon narrows to an aperture 141 (e.g., at or near theballoon nadir), then opens up again past that aperture, thereby defininga skirt structure opposing the balloon envelope across the aperture(e.g., below the aperture, such as shown by way of example in FIGS.4A-4C). The skirt 144 can be of unitary construction with the balloonenvelope (e.g., formed by a continuation along the length of the goresand load members), or can be of separate construction from the envelope(e.g., attached to the envelope, such as at or near the aperture, andpreferably forming a seal with the envelope). However, the passive ventcan additionally or alternatively include any other suitable ventstructures.

The passive vent preferably includes one or more closure mechanisms 145.The closure mechanism preferably functions (e.g., in the secondconfiguration) to seal the vent (e.g., preventing fluid exchange betweenthe balloon interior and the atmosphere). The closure mechanism can bearranged at or near (e.g., configured to close and/or seal at or near)the aperture 141, a location outside the balloon past the aperture, suchas the duct (e.g., at or near the external end 143, between the ductends, etc.), the skirt 144, and/or any other suitable structure, but canadditionally or alternatively have any other suitable arrangement.

In a first embodiment, the closure mechanism includes one or moredrawstrings (e.g., as shown in FIGS. 4A-4C and 5A-5D). The drawstringcan encircle an element to be closed, and an actuator can be operable totighten the drawstring, thereby sealing the vent at the encircledelement and transitioning the system from the first configuration to thesecond configuration.

In a second embodiment, the closure mechanism can include magneticelements. The magnets are preferably arranged on separate elements at ornear the location to be sealed (e.g., as shown in FIGS. 6A-6B and7A-7B). The magnets can include permanent magnets, electromagnets,and/or any other suitable magnets. In the first configuration, themagnets remain apart from each other (e.g., are held apart from eachother), and the passive vent remains open. In the second configuration,the magnets are allowed to come close to each other, such that theattractive magnetic force between them causes them to remain close(and/or come closer) and holds them together, thereby sealing the vent.In a first example, an actuator brings the magnets close enough toproduce a sufficient attractive force between the magnets that they sealthe vent. In a second example, an element holding the magnets apart isremoved or otherwise ceases to hold the magnets apart, and the magnetsare already in close enough proximity that in the absence of the elementholding them apart, they are strongly attracted to each other and arebrought together, sealing the vent. Additionally or alternatively, inexamples including one or more electromagnets, the electromagnets (or asubset thereof) can be deactivated in the first configuration, and canbe energized (e.g., magnetized) in the second configuration, thus givingrise to an attractive magnetic force that closes the vent. However, themagnetic closure mechanism can additionally or alternatively operate inany other suitable manner.

In a first example, the elements in or on which the magnets are arrangedcan be opposing sides of a duct, skirt, aperture, or other fluid passage(e.g., wherein bringing the magnets together causes the fluid passage tocollapse, thereby preventing fluid flow, such as shown by way of examplein FIGS. 6A-6B). In a second example, the first element can be at ornear the boundary of a fluid passage (e.g., around the boundary of anaperture 141, external end 143, etc.), and the second element can be asealing element, such as a flap (e.g., wherein bringing the magnetstogether causes the sealing element to be attached to the boundary ofthe fluid passage, thereby blocking the fluid passage), such as shown byway of example in FIGS. 7A-7B. However, the magnets can additionally oralternatively be arranged in any other suitable manner.

In a third embodiment, the closure mechanism includes one or moreadhesive elements configured to form a seal between multiple elements ator near the location to be sealed (e.g., having analogous placement asdescribed above with respect to the magnetic closure mechanism of thesecond embodiment). In this embodiment, at least one such element has anadhesive portion (e.g., configured to adhere to another of theelements). In the first configuration, the elements remain apart fromeach other (e.g., are held apart), and in the second configuration, theelements are brought into contact, thereby forming an adhesive seal thatkeeps the elements in contact and prevents fluid flow. In variations ofthis embodiment, the seal can analogously be formed using one or morehook-and-loop fasteners, van der Waals adhesion materials, and/or anyother suitable elements with adhesive-like properties.

In a fourth embodiment, the closure mechanism includes one or moreexpanding elements. The expanding element can be arranged within a fluidpassage (e.g., duct, aperture, etc). In the first configuration, theexpanding element does not block (or fully block) fluid flow within thepassage. For example, the expanding element can be configured in areduced volume configuration, can be arranged along a duct wall ratherthan blocking the duct's passage, and/or can otherwise be configured toallow fluid flow past itself. In the second configuration, the expandingmechanism preferably blocks fluid flow within the fluid passage. Forexample, the mechanism can expand (e.g., inflate) to fill orsubstantially fill the fluid passage, thereby preventing fluid flow.

However, the closure mechanism 145 can additionally or alternativelyinclude any other suitable fasteners, valve mechanisms, and/or otherclosure mechanisms.

In some embodiments, the passive vent can include one or more passivecheck valves. The check valve can function to permit gas flow out of theballoon but not into the balloon. In examples, the check valve caninclude one or more: ball valves, diaphragm valves, swing valves (e.g.,tilting disc valve), reed valves, collapsing-tube valves (e.g., duckbillvalve; duct hanging over a support, which can be kept open by gas flowout of the balloon, but is configured to collapse at or around thesupport when gas is not flowing out of the balloon; etc.). In passivevent embodiments including a check valve and no closure mechanism, thevent may not be operable to control the transition between differentconfigurations (e.g., it may always be possible for gas to vent from theballoon). Additionally or alternatively, the passive vent can includeone or more active valves (e.g., controllable between an open state andclosed state). In such embodiments, the check valve (and/or activevalve), in addition to or in place of a closure mechanism, can beresponsible for preventing atmospheric gas ingress into the balloon.

The exit to atmosphere of the passive vent (e.g., the duct external end)is preferably arranged at or near (e.g., just below, just above,substantially at, etc.) the height of the balloon nadir, but canalternatively be arranged substantially below the nadir. In the firstconfiguration, such an arrangement can enable maintenance of azero-pressure line near the balloon nadir (e.g., substantially at theheight of the vent exit). In a first example, the skirt aperture is atthe balloon nadir (e.g., as shown in FIG. 4A). In a second example,apertures formed in the balloon envelope gores are present near (e.g.,just above) the nadir. In a third example, the duct drops substantiallyto the height of the nadir (e.g., as shown in FIGS. 2A-2B). The ventexit can alternatively be arranged substantially above the nadir;however, such an arrangement may prevent retention of lift gas atheights below the vent exit, as the vent will typically work towardmaintaining the zero-pressure line at the height of the vent exit, andlift gas will typically flow out of the vent until the balloon is nolonger substantially inflated below the height of the vent exit.However, the vent can additionally or alternatively have any othersuitable arrangement.

In embodiments including vent ducts, the duct balloon end is preferablyarranged in a mid-height portion of the balloon, such as approximatelyhalfway up the balloon (e.g., halfway between the nadir and apex), suchas within a threshold distance (e.g., less than 5, 10, 15, 20, 25, or30% of the overall balloon height) of the midpoint. In sucharrangements, the aperture in the balloon envelope can be formed nearthe widest point of the gores, allowing for larger apertures (e.g.,substantially circular apertures) contained entirely within a singlegore. However, the duct balloon end can alternatively be arranged at anyother suitable height, can span multiple gores (such as by integratingthe load members into the passive vent at the point where they cross thepassive vent), and/or the passive vents can include any other suitableelements in any suitable arrangement.

3.1.3 Active valve.

The balloon 101 can optionally include one or more active valves 150.The active valve(s) can function to control partial venting of lift gas(e.g., to initiate balloon descent). In some examples, the active valves(and/or other actively-controlled venting elements) can include elementssuch as described in U.S. Provisional Patent Application 62/969,447,filed 3 Feb. 2020 and titled “Space Capsule”, which is hereinincorporated in its entirety by this reference (e.g., as described inU.S. Provisional Patent Application 62/969,447 regarding the ‘CrownValve’). The active valve(s) are preferably arranged at or near theballoon apex, but can additionally or alternatively be arranged at anyother suitable locations on the balloon. However, the valve(s) canadditionally or alternatively have any other suitable arrangement withinthe balloon, and/or the balloon can include no such valves.

3.1.4 Reefing sleeve.

The balloon 101 can optionally include one or more reefing sleeves. Atlow altitudes (e.g., altitudes at which the atmospheric pressure issignificantly greater than the pressure in the high-altitude range), theballoon is typically mostly uninflated, with a small inflated volume atthe top, and the uninflated portion of the balloon is typically foldedand/or twisted up (e.g., as shown in FIGS. 1C-1D). In some examples, thereefing sleeve can function to constrain some or all of this uninflatedportion. For example, the reefing sleeve can encircle (e.g., tightlyencircle, such as wrapping around) some or all of this uninflatedportion (e.g., as shown in FIG. 1D). The reefing sleeve can be releasedas the balloon inflates (e.g., can be torn open by the force generatedfrom expanding lift gas inflating the balloon, can be controlled torelease such as via one or more actuators, etc.).

In some examples (e.g., in which the passive vents are arranged in alower portion of the balloon, such as in an uninflated portion), thereefing sleeve may additionally or alternatively constrain (e.g.,encircle) the passive vents and/or portions thereof (e.g., before thereefing sleeve is released). For example, while constraining the vents,the reefing sleeve may constrict one or more fluid passages defined bythe vents, thereby limiting or preventing passage of gas through them(e.g., as described regarding ‘Closable balloon vent ducts’ and/or the‘reefing sleeve’ in U.S. Provisional Patent Application 62/969,447,filed 3 Feb. 2020 and titled “Space Capsule”, which is hereinincorporated in its entirety by this reference).

However, the balloon 101 can additionally or alternatively include anyother suitable elements in any suitable arrangement.

3.2 Payload.

The balloon system can optionally include one or more payloads 102. Thepayload is preferably mechanically connected to the balloon (e.g., by atether, rigid mechanical connection, etc.). The payload is preferablyconnected to the balloon proximal to the balloon nadir, but canadditionally or alternatively be connected in any other suitablelocation. In some examples, this connection can be a releasableconnection (e.g., can be operable to transition from a connectedconfiguration to a released configuration in which the mechanicalconnection between the payload and balloon is disconnected).

The payload 102 preferably includes a capsule (e.g., for containinghuman passengers), but can additionally or alternatively include anyother suitable elements. In examples, the payload 102 can include one ormore elements such as described in U.S. Provisional Patent Application62/969,447, filed 3 Feb. 2020 and titled “Space Capsule”, which isherein incorporated in its entirety by this reference (e.g., asdescribed in U.S. Provisional Patent Application 62/969,447 regardingthe ‘Capsule System’).

3.3 Safety Module.

The system can optionally include one or more safety modules 103, suchas parachutes, auxiliary propulsion systems (e.g., rockets such asretrorockets, propellers, jet engines, etc.), flight control surfaces(e.g., surfaces, such as fixed and/or rotary wings, including rigidwings, parasail wings, and/or any other suitable wings, rudders,ailerons, and/or elevators, configured to control vehicle flight, suchas powered or unpowered descent, in operation as an aerodyne), and/orany other suitable elements. The safety module can function to slowdescent of the system (e.g., in circumstances in which the propulsionmodule is not able to sufficiently slow system descent on its own, incircumstances in which the propulsion module fails and/or is detachedfrom the capsule, etc.), can function to reposition the system (e.g.,redirect capsule trajectory to ensure a water landing rather than aterrestrial landing), and/or can function to provide safety (e.g.,backup safety) for the system in any other suitable manner. The systemcan additionally or alternatively include any other suitable elements(e.g., as described in U.S. Provisional Patent Application 62/969,447,filed 3 Feb. 2020 and titled “Space Capsule”, which is hereinincorporated in its entirety by this reference, such as describedregarding the ‘Backup Descent System’).

However, the balloon system 100 can additionally or alternativelyinclude any other suitable elements in any suitable arrangement.

4. Method

The method 200 for balloon system operation is preferably performedusing the balloon system 100 described above. However, the method 200can additionally or alternatively be performed using any other suitablesystems.

4.1 Ascending.

The method 200 can optionally include ascending S210 (e.g., controllingthe balloon system to ascend). S210 can include ascending to a highaltitude range. This ascent is made from a lower altitude range,preferably a tropospheric altitude range, such as at or near the Earth'ssurface. In the low altitude range, the balloon is preferably partiallyinflated with the lighter-than-air fluid (e.g., wherein higheratmospheric pressures in this low altitude range prevent expansion ofthe lighter-than-air fluid to fully or substantially fully inflate theballoon). However, the balloon system can additionally or alternativelyascend from any other suitable altitude. In examples, this low altituderange can be less than 0, 0.1, 0.2, 0.5, 1, 2, 5, 7, 10, 15, 20, 25, or30 km above sea level, (e.g., at or substantially at ground level, suchas near sea level or ground level at the site at which the balloonsystem launches and/or lands), but can alternatively be in any othersuitable altitude range.

The high altitude range is preferably a stratospheric altitude range. Inexamples, the high altitude range can be more than 1, 2, 5, 7, 10, 15,20, 25, 30, 35, 40, or 50 km above sea level (e.g., above 30 km or100,000 ft), but can alternatively be in any other suitable altituderange. The balloon preferably inflates during ascent (e.g., due to thereduction in atmospheric air pressure during ascent), and preferablyreaches a fully or substantially fully inflated state at the highaltitude range (e.g., wherein the balloon remains substantially fullyinflated while remaining in the high altitude range). In examples, theballoon volume ratio (e.g., balloon volume at low altitude divided byvolume of the fully-inflated balloon) can be less than 1%, 2%, 3%, 5%,10%, 15%, 20%, 30%, 0.1-1%, 1-2%, 2-5%, 5-10%, 10-20%, 20-30%, 30-50%,or greater than 50%.

At low altitudes (e.g., altitudes at which the atmospheric pressure issignificantly greater than the pressure in the high-altitude range), theballoon is mostly uninflated, with a small inflated volume at the top,and the uninflated portion of the balloon is typically folded and/ortwisted up (e.g., as shown in FIGS. 1C-1D). In some examples, theballoon includes a reefing sleeve that encircles some or all of thisuninflated portion (e.g., as shown in FIG. 1D, as described above inmore detail, etc.). The reefing sleeve is preferably released (e.g.,automatically by the force of expanding lift gas inflating the balloon)during the ascent, but can additionally or alternatively be releasedwith any other suitable timing (and/or can be retained throughoutperformance of the method).

In a first embodiment, during the ascent, the passive vent is in thefirst configuration. In this embodiment, the vent may be open, therebyfluidly coupling the portion of the balloon interior adjacent the ventto a portion of the balloon exterior adjacent the vent. However, atsufficiently low altitudes (e.g., in which this portion of the balloonis uninflated and/or contained within a reefing sleeve), fluid transferbetween the balloon and atmosphere may be limited and/or prevented. Ifthe vent is arranged in the lower (uninflated) portion of the balloon,the vent will typically be sealed or restricted (e.g., because theballoon is twisted and/or folded up, because the reefing sleeve holdsthe vents closed, etc.). The reefing sleeve can be a sleeve encirclingthe uninflated lower portion of the balloon (and the passive vents orportions thereof, such as a portion of the vent duct). Additionally oralternatively, the negative-pressure condition in the balloon mayprevent the vent from fluidly coupling the balloon interior to theballoon exterior (e.g., by maintaining a passive check valve in a closedstate, by collapsing or preventing the opening of a vent structure suchas a duct, etc.). However, the partially inflated balloon canalternatively be configured in any other suitable manner.

In a second embodiment, the passive vent is configured in a closed state(e.g., the second configuration) during all or part of the ascent (e.g.,to be opened at higher altitudes, such as in the high-altitude range).In this embodiment, the passive vent is preferably operable totransition to the first configuration (e.g., from the secondconfiguration, or from a different configuration in which the passivevent is sealed). In this embodiment, the passive vent can be kept closedduring the ascent, and then the vent can be opened (e.g., transitionedto the first configuration) at higher altitude. This transition canoccur within the high-altitude range, or during a later portion ofascent to the high-altitude range (e.g., above a threshold relativeballoon pressure, such as once a negative-pressure condition does notexist in the balloon, does not exist at the vent aperture, or does notexist throughout the vent, or once a positive-pressure condition doesexist in the balloon; above a threshold altitude, such as an altitude atwhich atmospheric conditions transition from those in which mixing theatmospheric gases with the lift gas can pose an explosion risk to thosein which it cannot). In examples, the transition can occur at more than0.1, 0.2, 0.5, 1, 2, 5, 7, 10, 15, 20, 25, 30, 35, 40, or 50 km abovesea level (e.g., above 30 km or 100,000 ft), but can alternatively be atany other suitable altitude. However, the passive vent can additionallyor alternatively be configured in any other suitable manner duringascent.

4.2 Maintaining a zero pressure balloon condition.

Maintaining a zero-pressure balloon condition S220 preferably functionsto prevent any substantial pressure differential (e.g., positivepressure) from forming within the balloon interior, as a substantialpositive pressure within the balloon could pose a risk of rupturing theballoon. S220 is preferably performed while in the high-altitude range,such as while maintaining the balloon in the high-altitude range (e.g.,substantially maintaining altitude within the high-altitude range). S220is preferably performed during all or substantially all of the timespent residing in the high-altitude range, but can additionally oralternatively be performed at any other suitable times. In examples, theballoon can remain in the high-altitude range for a time period ofminutes, hours, days, or longer. In one example, the balloon remains inthe high-altitude range between 1 and 10 hours (e.g., 2-6 hours), suchas entirely or partially during the daytime. However, the balloon canremain in the high-altitude range and/or be maintained in thezero-pressure condition for any other suitable period of time.

During flight of a typical zero-pressure balloon, the balloon becomesmore inflated as it ascends; once the balloon is fully inflated, it willtypically vent excess lift gas (the free lift) in order to maintain asubstantially zero-pressure condition. After venting the free lift, theballoon typically remains substantially fully inflated while maintainingaltitude in a high-altitude range. During this time, the lift gas mayincrease and/or decrease in temperature. As the lift gas heats (e.g.,due to solar irradiation, such as during the day), the lift gas expandswhich can cause the balloon to become slightly more inflated, therebyresulting in an altitude increase. In response to the gas expansion,some gas can vent from the balloon (e.g., through one or more passivevents, such as vent ducts in the balloon). This venting preferablyoccurs rather than having the gas expansion result in a substantialpositive pressure within the balloon (e.g., which could occur once theballoon is completely inflated, in the absence of sufficient passiveventing). As the lift gas cools (e.g., due to a reduction in or theabsence of solar irradiation, such as during the night), the lift gascontracts and the balloon becomes slightly less inflated, therebytypically resulting in an altitude decrease (which can be compensatedfor by releasing ballast).

Accordingly, S220 preferably includes maintaining one or more passivevents in the first configuration, thereby enabling passive venting oflift gas (e.g., venting of the free lift near the end of the ascentand/or beginning of altitude maintenance, venting of heated lift gasduring altitude maintenance, etc.). If a passive vent is not in thefirst configuration (e.g., if ascending S210 is performed with the ventsin the second configuration or some other closed configuration), thenS220 preferably includes transitioning the vents to the firstconfiguration (e.g., opening and/or unsealing the vents); without such atransition, the balloon may enter a substantially over-pressure state,which can pose a risk of balloon rupture.

However, S220 can additionally or alternatively include maintaining thezero-pressure balloon condition in any other suitable manner.

4.3 Sealing Balloon Vents.

Sealing balloon vents S230 preferably functions to prevent atmosphericgas ingress into the balloon interior, as a mixture of atmosphericoxygen with a hydrogen lift gas could pose an explosion risk. S230 ispreferably performed for embodiments of passive vents that include aclosure mechanism (in passive vent embodiments including only a checkvalve, the vents are automatically sealed against atmospheric gasingress by the check valve, and do not include a closure mechanism thatcan be used to actively seal the vents). S230 preferably includesclosing and/or sealing all passive vents of the balloon, transitioningeach passive vent to the second configuration (e.g., from the firstconfiguration), but can alternatively be performed only for a subset ofsuch vents. This transition can be controlled (e.g., effected) asdescribed above regarding the passive vents S140 and/or in any othersuitable manner.

S230 is preferably performed once the risk of balloon overpressure (inthe absence of passive venting) no longer exists (or once this risk issufficiently low). In examples, this could be once the balloon is nolonger fully inflated and is not expected to become fully inflated,and/or once the lift gas is not expanding (and is not expected to expandfurther). Alternatively, S230 can be performed before these conditionsare strictly met, such as when a substantial positive pressure conditionis unlikely to arise (e.g., the balloon may become fully inflated, butonly minimal positive pressure is expected to exist; lift gas may beexpanding or expected to expand in the future, but is expected not toexpand sufficiently to fully inflate the balloon or create a substantialpositive pressure; etc.).

S230 is preferably performed in temporal proximity to initiation ofdescent (e.g., as described below in more detail). For example, theballoon vents can be sealed just before, just after, and/orsubstantially concurrent with initiation of descent (e.g., within athreshold time of descent initiation, such as within 1, 2, 5, 10, 20,30, or 60 minutes, etc.).

In a first embodiment, S230 is performed substantially concurrent withthe beginning of descent. A positive rate of descent can be indicativethat the balloon is not fully inflated (e.g., a negative-pressurecondition exists within part or all of the balloon), and so the balloonvents are preferably sealed at this time to prevent air ingestion. In analternate variation of this embodiment, S230 can be performed afterdescent has begun, but before the balloon has descended to an altitudewith atmospheric pressure high enough to pose a potential explosion risk(e.g., a mixture of hydrogen with the atmosphere under the presentconditions would not form an explosive gas). In this embodiment, thelift gas will compress into a smaller volume during descent, and so therisk of overpressure within the balloon after vent closure is typicallyminimized or eliminated.

In a second embodiment, S230 is performed at a time when the lift gastemperature is dropping and is not anticipated to rise before balloondescent is initiated. For example, S230 can be performed after the sunhas set, such as in situations in which the descent will be initiatedbefore sunrise. In this embodiment, the lift gas is not expected toexpand (e.g., will lose volume as it cools), and will later be subjectto higher atmospheric pressures at lower altitudes once descent begins,and so the risk of establishing an overpressure condition in the balloonafter vent closure is reduced or eliminated.

S230 can alternatively be performed at any other suitable time beforethe risk of substantial air or oxygen intake arises. For example, S230can be performed while the balloon is still in a region with lowatmospheric pressure, such that the atmospheric oxygen concentration isinsignificant (e.g., and so sufficient oxygen to pose a hydrogenexplosion risk is unlikely to enter the balloon interior) and/or suchthat the balloon is still mostly inflated (e.g., and thus, a largenegative pressure has not been established within the balloon interior).This may be within the same altitude range described above at which thepassive vents may become open (e.g., due to release of the reefingsleeve, due to transition of the vents to the first configuration,etc.), at a higher altitude range, at a lower altitude range, and/or atany other suitable altitude.

However, S230 can additionally or alternatively be performed with anyother suitable timing and/or can include sealing the balloon vents inany other suitable manner.

4.4 Descending.

The method preferably includes descending S240 (e.g., descending fromthe high altitude range). The descent is preferably made to atropospheric altitude range (e.g., less than 0, 0.1, 0.2, 0.5, 1, 2, 5,7, 10, 15, or 20 km above sea level), such as to or near the Earth'ssurface, but can alternatively be made to a lower stratospheric altitude(e.g., less than 7, 10, 15, 20, 25, 30, 35, 40, or 50 km above sealevel) or to any other suitable altitude. For example, the descent canbe made in preparation for landing the balloon system. During descent, amajority of the lighter-than-air fluid is preferably retained within theballoon. Despite this retention, the balloon will typically partiallydeflate during the descent, due to the increase in atmospheric airpressure.

S240 preferably includes initiating the descent. The descent ispreferably initiated by actively controlling the balloon to ventadditional lift gas (e.g., additional to the lift gas that is passivelyvented through the passive vents). The additional lift gas is preferablyvented from any location at or near the balloon apex. For example, S240can include controlling a valve arranged at or near the apex to open,thereby allowing lift gas to vent through it.

As described above, S230 can be performed after initiating descent(e.g., once the rate of descent is greater than the threshold velocity,such as 0, 0.1, 0.2, 0.5, 1, 2, or 3 meters/second, etc.). However, S230and S240 can additionally or alternatively be performed with any othersuitable timing (with respect to each other and/or any other suitableevents).

4.5 Additional Balloon Operations.

The method 200 can optionally include one or more elements such asdescribed in U.S. Provisional Patent Application 62/969,447, filed 3Feb. 2020 and titled “Space Capsule”, and/or in U.S. patent applicationSer. No. 17/162,151, filed 29 Jan. 2021 and titled “Aerospace BalloonSystem and Method of Operation”, each of which is herein incorporated inits entirety by this reference. For example, the method can include oneor more elements described in U.S. patent application Ser. No.17/162,151 regarding the method described therein (e.g., regarding‘operating the balloon system in flight’, ‘landing the balloon system’,and/or ‘deflating the balloon’), and/or one or more elements describedin U.S. Provisional Patent Application 62/969,447 regarding balloonsystem operation (e.g., as described regarding ‘Launch and Recovery’and/or ‘Buoyancy control’). However, the method 200 can additionally oralternatively include performing any other suitable balloon systemflight operations, and/or can include any other suitable elementsperformed in any suitable manner.

An alternative embodiment preferably implements the some or all of abovemethods in a computer-readable medium storing computer-readableinstructions. The instructions are preferably executed bycomputer-executable components preferably integrated with acommunication routing system. The communication routing system mayinclude a communication system, routing system and a pricing system. Thecomputer-readable medium may be stored on any suitable computer readablemedia such as RAMs, ROMs, flash memory, EEPROMs, optical devices (CD orDVD), hard drives, floppy drives, or any suitable device. Thecomputer-executable component is preferably a processor but theinstructions may alternatively or additionally be executed by anysuitable dedicated hardware device.

Although omitted for conciseness, embodiments of the system and/ormethod can include every combination and permutation of the varioussystem components and the various method processes, wherein one or moreinstances of the method and/or processes described herein can beperformed asynchronously (e.g., sequentially), concurrently (e.g., inparallel), or in any other suitable order by and/or using one or moreinstances of the systems, elements, and/or entities described herein.

The FIGURES illustrate the architecture, functionality and operation ofpossible implementations of systems, methods and computer programproducts according to preferred embodiments, example configurations, andvariations thereof. In this regard, each block in the flowchart or blockdiagrams may represent a module, segment, step, or portion of code,which comprises one or more executable instructions for implementing thespecified logical function(s). It should also be noted that, in somealternative implementations, the functions noted in the block can occurout of the order noted in the FIGURES. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently, or theblocks may sometimes be executed in the reverse order, depending uponthe functionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the preferred embodiments of the invention withoutdeparting from the scope of this invention defined in the followingclaims.

I claim:
 1. A balloon system comprising: a zero-pressure balloondefining a balloon interior configured to contain a lighter-than-airfluid; an active valve arranged at a surface of the zero-pressureballoon, the active valve operable to controllably fluidly couple theballoon interior to a balloon exterior via the active valve; a passivevent arranged at the surface of the zero-pressure balloon, the passivevent operable to transition from a first configuration to a secondconfiguration, wherein: in the first configuration, the balloon interioris fluidly coupled to the balloon exterior via the passive vent,wherein, in the first configuration, the passive vent is configured topassively maintain a substantially zero pressure condition within theballoon; and in the second configuration, the passive vent issubstantially sealed.
 2. The system of claim 1, wherein: the ballooncomprises a balloon apex and a balloon nadir; the passive vent defines avent exit; and the vent exit is arranged proximal the balloon nadirrelative to the balloon apex.
 3. The system of claim 2, wherein: theballoon defines a primary axis from the balloon nadir to the balloonapex; the balloon defines a nadir reference plane normal to the primaryaxis, wherein the balloon nadir lies substantially on the nadirreference plane; and the nadir reference plane is arranged between thevent exit and the balloon apex.
 4. The system of claim 2, wherein: thezero-pressure balloon is inflated by the lighter-than-air fluid; and thevent exit is not arranged substantially above the balloon nadir relativeto a gravity vector.
 5. The system of claim 4, wherein: the balloondefines an inflated portion and an uninflated portion, the inflatedportion arranged above the uninflated portion relative to the gravityvector; and the system further comprises a reefing sleeve encircling theuninflated portion and at least one portion of the passive vent, therebypreventing ingress of atmospheric gasses into the balloon interior viathe passive vent.
 6. The system of claim 5, wherein the least oneportion of the passive vent comprises the vent exit.
 7. The system ofclaim 5, wherein the reefing sleeve is configured to rupture, such thatthe reefing sleeve does not encircle the uninflated portion and the atleast one portion of the passive vent, in response to a pressureincrease within the balloon.
 8. The system of claim 1, furthercomprising a reefing sleeve, wherein the reefing sleeve encircles atleast one portion of the balloon and at least one portion of the passivevent, thereby preventing ingress of atmospheric gasses into the ballooninterior via the passive vent.
 9. The system of claim 1, wherein: whilein the first configuration, the passive vent is configured to maintain asubstantially zero pressure condition within the balloon by passivelyventing lighter-than-air fluid via the passive vent; and after passivelyventing lighter-than-air fluid via the passive vent, the passive vent isconfigured to transition to the second configuration, such that theballoon interior is not fluidly coupled to the balloon exterior via thepassive vent.
 10. The system of claim 9, wherein the active valve isconfigured to initiate descent of the system by opening, therebyactively venting lighter-than-air fluid via the active valve.
 11. Thesystem of claim 10, wherein the passive vent is configured to transitionto the second configuration after the active valve initiates descent ofthe system.
 12. The system of claim 1, wherein: the passive vent definesa fluid passage between the balloon interior and an environmentsurrounding the balloon; the passive vent comprises an inflatable memberarranged within the fluid passage; and the passive vent is operable totransition from the first configuration to the second configuration byinflating the inflatable member such that the inflatable member sealsthe fluid passage.
 13. The system of claim 1, wherein the passive ventcomprises: a closure mechanism, the passive vent is operable totransition from the first configuration to the second configuration byactuating the closure mechanism; and a check valve separate from theclosure mechanism, wherein, when the passive vent is configured in thefirst configuration, the check valve is configured to permit fluid flowthrough the passive vent from the balloon interior to an environmentsurrounding the balloon and is configured to substantially prevent fluidflow through the passive vent from the environment to the ballooninterior.
 14. The system of claim 1, wherein: the passive vent comprisesa check valve between the balloon interior and an environmentsurrounding the balloon; in the first configuration, the check valve isopen; in the second configuration, the check valve is closed; and thepassive vent is configured to automatically transition from the firstconfiguration to the second configuration in response to fluid flowthrough the passive vent from the environment to the balloon interior.15. The system of claim 1, wherein: the passive vent comprises: a firstmember comprising a first magnet; and a second member comprising asecond magnet; the passive vent defines a fluid passage between thefirst and second members; in the first configuration, the first andsecond members are not in contact; and in the second configuration, thefirst and second magnets hold the first and second members in contact,thereby sealing the fluid passage.
 16. The system of claim 1, wherein:the balloon defines an aperture at a nadir of the balloon; the passivevent comprises: a skirt extending downward from the aperture; and adrawstring encircling the skirt; and the passive vent is operable totransition from the first configuration to the second configuration bytightening the drawstring around the skirt.
 17. A method for operating aballoon system, comprising, at a zero-pressure balloon defining aballoon interior configured to contain a lighter-than-air fluid: while apassive vent of the zero-pressure balloon is in a first configuration,in which the balloon interior is fluidly coupled to a balloon exteriorvia the passive vent, passively venting a first portion of thelighter-than-air fluid via the passive vent, thereby maintaining asubstantially zero pressure condition within the balloon; afterpassively venting the first portion of the lighter-than-air fluid viathe passive vent, initiating a balloon descent, comprising controllingan active valve of the balloon system to open, thereby actively ventinga second portion of the lighter-than-air fluid via the active valve,wherein the active valve is distinct from the passive vent; and afterpassively venting the first portion of the lighter-than-air fluid viathe passive vent, configuring the passive vent in a secondconfiguration, in which the balloon interior is not fluidly coupled tothe balloon exterior via the passive vent, comprising sealing thepassive vent.
 18. The method of claim 17, further comprising, beforepassively venting the first portion of the lighter-than-air fluid viathe passive vent, ascending substantially from ground level to a highaltitude range while the passive vent is configured in the firstconfiguration.
 19. The method of claim 17, wherein the balloon defines aballoon nadir, wherein the passive vent defines a vent exit, wherein thevent exit is not substantially higher than the balloon nadir withrespect to a gravity vector.
 20. The method of claim 17, whereinconfiguring the passive vent in the second configuration is performedafter initiating the balloon descent.
 21. The method of claim 20,wherein configuring the passive vent in the second configuration isperformed in response to determining that balloon descent has initiated.